Do Preoperative Depressor Anguli Oris Muscle Blocks Predict Myectomy Outcomes? A Single-Cohort Comparison in Postparetic Facial Synkinesis.

ABSTRACT

SUMMARY: The complexity of facial synkinesis will likely benefit from an individualized approach to intervene on discrete synkinetic facial subunits. This overarching treatment algorithm requires understanding each synkinetic mimetic subunit. The depressor anguli oris muscle, because of its antagonistic relationship to the zygomaticus major, is of particular interest. This study aims to provide outcomes of depressor anguli oris muscle myectomies and the predictive value of preoperative lidocaine blocks. Preoperative depressor anguli oris muscle lidocaine blocks were administered to patients with postparetic facial synkinesis, and subsequent isolated depressor anguli oris muscle myectomies were performed on those who showed improvement and elected to proceed. Twenty synkinetic patients underwent isolated depressor anguli oris myectomies after lidocaine blockade, with an average follow-up of 9 months. Facial mimetic parameters and measurements were recorded and analyzed by Massachusetts Eye and Ear Infirmary Emotrics and National Institutes of Health ImageJ software to compare results from both blocks and myectomies. Both lidocaine block and depressor anguli oris myectomy improved dental show by 14.42 mm 2 and 23.012 mm 2 , respectively, and open mouth smile angles above a horizontal plane by 4.66 and 3.32 degrees, respectively. There was no statistical difference between the groups in terms of improvements noted in closed and open mouth smile angles above a horizontal plane, or in dental show ( p = 0.695, p = 0.351, and p = 0.242, respectively). Preoperative lidocaine blockade accurately predicts the improvement in dental show and modiolus smile angle that is provided by isolated depressor anguli oris muscle myectomy. This furthers our understanding of depressor anguli oris muscle abnormality in the overall spectrum of facial synkinesis. CLINICAL QUESTION/LEVEL OF EVIDENCE Therapeutic, IV.